The present invention relates in general to a refrigerant compressor for air-conditioning or similar systems, and more particularly to a variable-delivery refrigerant compressor which is capable of automatic adjustment of compression capacity or displacement by rendering inoperative selected one or some of plural discharge valves which correspond to respective plural compression chambers.
Such type of variable-delivery compressor is known according to a laid-open publication No. 57-73877 of a Japanese Patent Application filed in the name of the assignee of the present application. In the compressor disclosed in this publication, there is disposed an actuator which is movable between its normal and shifted positions. With the actuator held in its normal position, all of plural discharge valves of the compressor are rendered operative to perform their normal valving function. In the shifted position, selected one or some of the discharge valves are rendered inoperative. The actuator is biased by a spring toward its shifted position for low-capacity operation of the compressor, and moved from its shifted position toward its normal position by a discharge pressure of the compressor against a biasing force of the spring so that the delivery of the compressor is increased to its high-capacity level.
In the compressor of the type described above, a solenoid switch valve is employed to control a supply of refrigerant of a discharge pressure to the actuator. The use of the solenoid switch valve inherently increases weight and cost of manufacture of the compressor, and needs electrical controls for actuating the solenoid to operate the valve according to variation in the delivery required, thus requiring the input of a considerable amount of electric energy.
The above inconveniences of the compressor known in the art will be encountered also in the following arrangements which the present applicants regard as alternatives to the above-discussed known arrangement wherein discharge valves are moved axially of the compressor between their normal and shifted positions. The first possible alternative is an arrangement wherein discharge valves are shifted laterally from their normal operative position opposite to corresponding discharge ports to their inoperative position which is spaced from the operative position radially or circumferentially of the compressor. The second alterative may be an arrangement for preventing discharge valves in their open position from returning to their closed position and thereby disabling then to perform their normal valving function, rather than shifting the discharge valves themselves. As another alternative arrangement, it is possible that a spring-biased single-acting cylinder used in the known actuator be replaced by a double-acting cylinder with a piston which receives a discharge pressure of the compressor selectively at one of their opposite faces. Another possibility of modification is to use a rotary actuator in place of a linearly operated actuator used in the known compressor. As pointed out before, all of these alteratives which come into the applicants' mind suffer the same inconveniences as experienced by the known compressor.